This invention pertains to sonar antennas designed to be loaded onto an underwater device in order to form an inserted head of that device and a method for manufacturing these antennas.
The technical field of the invention is that of the assembly of sonar antennas for acoustic homing devices on underwater devices, especially torpedos.
A sonar antenna is a collection of electro-acoustic transducers, for instance, piezo-electric transducers, which are arranged in a network to transmit acoustic waves in water, or to receive acoustic waves which are echos of transmitted waves, or which are waves transmitted by a target.
To this day, sonar antennas used in underwater devices are comprised of a mosaic of transducers which are arranged inside the cone-shaped head of the device. The transducers are supported on a plug, which may or may not be removable, by a material having an acoustic impedance as different as possible from that of the plug, so as to acoustically decouple the antenna from the hull of the device upon which the plug is affixed.
This familiar type of assembly has certain disadvantages. The support surface which carries the transducers is a flat surface which also serves as the forward bulkhead of the device. This flat surface therefore must withstand the high hydrostatic pressure to which devices designed for deep submersion are subjected. Since this surface is flat, it must have a very significant mass to withstand such pressures.
Furthermore, since the transducer support is part of the device's resisting structure, the transducers are placed in contact with or close to that structure, and therefore are subjected to the parasitic vibrations which are induced in that structure by the device propeller and by water flow disturbances along the hull. Thus, in the traditional embodiments, there is an intimate mechanical link brought about by hydrostatic pressure between the transducer supports and the device's resisting structure.